An in situ method for remediating Cs-137-contaminated wetlands using naturally occurring minerals

Cesium's enhanced bioavailability in contaminated wetlands on the U.S. Depa rtment of Energy's Savannah River Site (SRS) is thought to be due to the lo w clay fraction of SRS soils, and that the clay mineralogy is dominated by kaolinites. Remediation of the wetlands is problematic because current tech nologies are destructive to the sensitive ecosystems. We tested I I clay mi nerals (two micas, a vermiculite, six illites, a kaolinite, and a smectite) for their propensity to sorb and retain Cs-137. Two minerals were subseque ntly chosen as candidates for in situ remediation amendment materials becau se they had 137Cs distribution coefficients (K-d) well in excess of 10,000 ml.g(-1), and desorbed less than 20% of the Cs when mixed in a 0.1 M NH4Cl solution. Incremental additions of the candidate minerals to Cs-137-contami nated sediments appreciably intercepted and retained desorbed Cs-137 in the presence of high levels of NH4. Implications for using the minerals as a n ondestructive, in situ remediation technique are discussed.